1. Field of the Invention
The present invention relates to protective boots, and particular, to boots constructed for environmental protection and outdoor winter sports usage. The invention is intended to greatly reduce the weight to enhance winter athletic performance at greatly reduced cost.
2. Prior Art
The modern winter boot, particularly those used for hunting, ice fishing, snow shoeing, winter hiking, snow boarding, skiing, dog sledding, in-line skating and serious climbing are made up of a combination of many elements that have specific functions, all of which must work together for the support and protection of the foot. Winter sport boots today are varied in both design and purpose. Ski boots, Snowboard boots, winter hikers, snow shoeing boots, hunting boots, ice fishing boots, dog sledding boots, etc. all are designed to be used in very specific, and very different ways. They are also designed to provide a unique and specific combination of traction, warmth, water proofness, support and environmental protection to enhance performance. Not only are boots designed for specific sports, they are also designed to meet the specific characteristics of the user. For example, boots are designed differently for heavy duty usages than for light duty usages. The sport of skiing, versus ice fishing, impose totally different structural loads on the boot shell construction. It is therefore important to be able to adjust the characteristics of the various possible structural shell designs of the boot to accommodate these factors. It is also desirable to be able to minimize the weight of such structural shell designs so as to enhance outdoor winter performance (as well as summer usages.)
Generally, a protective boot is divided into 3 or 4 parts; the traction system, the shell, the upper, and the insulation or liner system (if applicable.) The traction system is generally natural rubber or a variety of synthetics (such as polyurethane) or co-polymers of both natural and synthetic elastomers. The insulation (if applicable) is produced as a xe2x80x9chung liningxe2x80x9d inside the upper and shell, or consists of a removable liner or xe2x80x9cbootie.xe2x80x9d The xe2x80x9cupperxe2x80x9d may be of leather or synthetic materials (in the case of xe2x80x9cPac Bootsxe2x80x9d) or plastic (in the case of a Ski Boot xe2x80x9cCuffxe2x80x9d.) Various upper constructions are possible, and in use at this time.
It is the shell, that we are most interested in exploring herein. Basically, five different types of shells exist today; an injection molded plastic shell (ski boots, in-line skates, serious climbing boots, etc.) an injection molded rubber (or synthetic) shell (pac boots, cycling boots, etc.), a vulcanized rubber shell (pac boots, waders, etc.), dipped rubber (or synthetic) shell footwear (ice fishing, waders), and injected polyurethane foam shell footwear (pac boots, etc.) Centrifugally molded footwear is scarce to non-existent in today""s marketplace.
The function of the shell is the most crucial of all of the components that make up protective boots, particularly for outdoor sports usage. For ice fishing, the shell must be wind proof and waterproof. For skiing, the shell must be wind proof, water/snow proof, and also highly structural (stiff.) Abrasion and cut/tear resistance is also important Sunlight/UV protection and chemical resistance must be also considered. Cold crack flexibility and heat resistance are also required.
The integration of the shell to the other components of the boot (upper, midsolexe2x80x94if applicable and outersole) are also key considerations. For example, Pac Boots require that the shell contain a stitch flange (for sewing through) to enable attachment of the upper. Ski boots require that the shell be able to anchor and secure rivets for attachment of the (ankle) cuff. In-line skates require the same, of their shell. Bonding is also required for attachment of uppers as well as outersoles, Some pac boots incorporate xe2x80x9ctextile fibre knit socksxe2x80x9d attached to the inside surface to reduce the surface friction within the shell assembly.
To achieve adequate shell functionality, as well as integration into the various end usages of the completed boots, is a daunting task. There are many limiting factors faced by today""s designer. Among them are the following process limitations (with all currently used processes:)
1. The thickness of the shell is too great at all of the xe2x80x9cminimum desired thicknessxe2x80x9d areas (most of the whole shell.)
2. The shell is too heavy to achieve enough weight reduction for highly active sports usage.
3. The costs of finished parts as well as molds is very very high.
4. Mold series production time is too long.
1. The shell must be produced in two parts, rather than one.
2. Thermoplastic welding is required to integrate the shell halves.
3. Weld reliability is always suspect, especially for cold weather impact and flexibility requirements.
4. Very few available materials exist in sheet form, for this process.
5. Parts are too expensive.
1. All corners of parts are too thick, due to process.
2. Pars are too heavy, due to above.
3. Parts are too expensive.
1. Deep 3D shape of parts is not achievable at all.
2. Proper materials are not sensitive to RF.
Injection molded boot shells are well known to the art. For example, U.S. Pat. No. 4,253,251, to Salomon, describes a rigid shelled ski boot containing an internal foot restraint system. The shell itself is too thick, too heavy, and too expensive for any sport except skiing. U.S. Pat. No. 4,279,044, to Colquaud, describes a polyurethane molding process which involves a 3 step xe2x80x9cinsert moldingxe2x80x9d process for sandals. This process cannot produce truly functional cold weather outdoor boot shells.
U.S. Pat. No. 5,647,150, to Romanato et al., describes an injection molding process for footwear shells, whereby a fabric sock becomes molded to the inside surface of the boot shell. Again, since the shell is injection molded, it is too thick, too stiff, and too expensive for anything but alpine ski boot usage. Additionally, U.S. Pat. No. 5,575,091, to Mattiuzzo, describes another injection molded ski boot application, this time employing a boot cuff with a rigidizing insert. Once again, an ultra stiff, heavy, and expensive boot shell results. U.S. Pat. No. 4,266,750, to Gallizia, describes a process for producing elastomeric boot shells but not plastic. Three separate shells are molded together, via an internal expandable bladder. This process produces boots far too heavy and expensive, only from non-plastic (elastomeric material.)
Additional prior art references relevant to this invention are:
U.S. Pat. No. 4,255,825, to Rigon, describes another injection molding process for plastic boots with rigid high heels.
U.S. Pat. No. 4,302,889, to Negrin, describes a boot to be worn after skiing. The novel feature here, seems to be the internally suspended lining system, within a shell.
U.S. Pat. No. 4,286,936, to Hustedt, describes an injection casting apparatus for shoe soles only. This process cannot produce a completed boot shell.
U.S. Pat. No. 4,224,708, to Becka, describes a machine for molding and flanging only the uppers of shoes. Again, this machine cannot produce a completed boot shell.
U.S. Pat. No. 4,266,314, to Londner espouse Ours, describes a method of manufacture of sports shoes involving two overlapping portions of plastic material overmolded onto a lining material, formed into the shape of a slipper. Adding a sole comprises a third step of this operation. This invention is far to labor intensive to be competitive in today""s markets.
Furthermore, U.S. Pat. No. 4,301,564, to Dalebout, describes a novel method for producing inner boots that fit within an outer shell, but falls short of defining a process which produces the shell itself.
It is an object of this invention to provide a method for producing outdoor boot shells that can be as thin as 0.25 mm. Currently, no other method can produce them less than 1.0 mm thick on a consistent basis. In most cases, 1.5-2.0 mm is un-achievable.
It is a further object of this invention to provide a method for producing outdoor boot shells that can weight as little as 40 grams. Currently, no other method can produce them less than 100-140 grams.
It is a further object of this invention to provide a method for producing outdoor boot shells that cost xc2xd (half) the cost of any other process.
It is still a further object of this invention to provide a method for producing the molds for the boot shells at a quicker rate, as well as a lower cost.
The foregoing primary objects of this invention are achieved by producing a coreless mold consisting only of mold cavities (no cores.) Two or more cavity sections may be used. The mold sections are also provided with an opening for the insertion of gas pressure. The mold sections are further provided with a spring loaded set of pinch bars. The mold sections are still further provided with a circumferential xe2x80x9cpinch-off die edge,xe2x80x9d located around (at) the parting line of the mold sections.
Additionally, the primary objects of this invention are achieved by positioning the above mold in such a way(s) that it can receive an extruded thermoplastic or thermoset parison (cylinder shaped length) of extruded material and incorporate a pressurization attachment, so as to allow inflation of the parison so as to fill out the mold cavity shape. Once the part is cool, it can be ejected and trimmed.
A preference of this invention is to employ an extrusion source that can be computer controlled so as to be able to vary the parison thickness across its length (circumferential bands.)
A further preference of this invention is to employ extrusion die head tooling that allows xe2x80x9cstripingxe2x80x9d (vertical bands) so as to be able to vary the thickness of the parison along its length also.
An objective of this invention is to allow quicker processing times (in the mold) for each boot shell. This is achieved since the thinner material allowed by the process can be cooled much quicker (and with less shrinkage, as well) than the thicker parts produced by other processes.
A still additional object of this invention is to be able to over-mold inserts which are pre-placed inside of the mold, prior to capturing the parison within the mold. These inserts may consist of rubber tread elements of the outersole, rigidizing stiffeners at selected locations, or decorative elements, etc.
A still further additional object of this invention is to be able to simultaneously mold a pair (left and right) of boots from the same parison, using only one mold in which to do it. This is accomplished by using a larger diameter parison (than required for producing only one boot.) Also, the single mold utilized employs cavities for both left and right boot shells. The cavities are joined at the entry hole (for the foot) at the top of each boot. The pair is molded in one shot and separated into a left and right boot via a single trim line which connects the pair of boots during the molding process only.
Additionally, an object of this invention is to provide a boot shell that can employ a textile fiber covered inside surface in order to control the surface friction inside of the shell. This is accomplished by a secondary process called xe2x80x9cflocking.xe2x80x9d Flocking of the inside surface requires a special adhesive and conductive grounding system for the cement laden inside surface of the boot shell, which is pre-sprayed before the ground textile fibers (xe2x80x9cFlockxe2x80x9d) is introduced, Both adhesive and flock are introduced through the xe2x80x9cblow holexe2x80x9d of the shell which is automatically present, due to the blow molding process utilized here. An electrostatic spray gun is used to introduce the flock into the boot shell, before the boot shell foot opening is trimmed off.
A final objective of this invention is to be able to eliminate the high cost of excess material which is trimmed from the part after molding (flashing.) As an example, in the injection molding process, only a small portion of the flashing can be reground and reused. Typically a maximum of 5% of the reground material is usable, without adversely affecting the properties of the virgin material which it is added to.
This objective was attained by reducing the shear forces, experienced by the material during extrusion and molding processes to the point thatxe2x80x94if the material is not scorched (over heated)xe2x80x94the flashing can be trimmed off, reground, and mixed into virgin material at a 100% regrind rate. This is not possible in any other process.
A further objective of this invention is to produce a boot shell which may employ either an internal or an external midsole/wedge material in order to provide heel lift for the foot, both internally and externally (to the shell) or either/or.
The foregoing and other objects, features, and advantages of this invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.